摘要:

Two studies of the perceptual effects of low-power plus lenses were done on groups of young-adult binocular emmetropic observers. The first study used visual masking to induce short-term perceptual stress in two groups of 10 observers: one group wore piano lenses and the other wore +0.50 D lenses. No significant differences in visual perceptual performance were found between these groups. The second study used a more natural letter-search task and rotated 18 observers through nine lens powers from piano to +1.0 D in + 0.12D steps, to form a test of the hypothesis that “critical” lens power benefits individual observers. Other conditions in the study were arranged to maximize the positive effect of short-term wear of plus lenses, if one was found. Results showed neither an overall group benefit from a particular power of plus lens nor an individual lens power that benefited each individual observer. These data showed a strong practice effect over the nine experimental sessions, regardless of lens power, that could account for earlier reports in the literature of positive results from using these lenses.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The changes in central and peripheral corneal thickness and topography during initial (1 st-day) wear, adaptation to, and long-term wear of the Dura Soft lens were monitored in a group of 10 patients. Monitoring was by means of the electronic digital pachometer and the photoelectronic keratoscope (PEK). A variety of physiological responses to lens wear was noted in individual patients, but generally the changes occurring were comparable to those reported for other soft lenses. These changes consisted of an average increase of 5–6% in central and peripheral corneal thickness during the initial phase of wear and 4–5% during adaptation; this was followed by a reduction with long-term wear to 2–3%. Corneal topography was relatively stable throughout the period of the study.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

A simple reaction time paradigm was used to study binocular interactions for suprathreshold grating patterns before and after 8 days of constant monocular occlusion. Prior to patching, subjects demonstrated binocular summation for near threshold contrast stimuli and binocular summation and facilitation for high contrast stimuli. After the period of occlusion, the subjects showed binocular inhibition for high contrast stimuli but still demonstrated binocular summation for low contrast stimuli. The effects of occlusion were reversible and appear to be related to an oculomotor imbalance.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Previous work dealing with the question of whether or not the eyes of small mammals are hyperopic has been restricted largely to the study of nocturnal animals such as the rat. In this study, refractive state of the eye of a small diurnal mammal, the ground squirrel, was measured by retinoscopy and from the electrophysiological response of retinal ganglion cells to grating targets. Both measurements show the squirrel to be emmetropic. We conclude that the refractive state of the eye is not a function of eye sizeper se, but rather a function of whether the animal is nocturnal or diurnal.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Three formulas are given and derived which can be used to evaluate the relationship between image vergence and object position for any two-lens system and will be very useful in the special case of telescopes. A corresponding formula for afocal telescopes has been published previously. The formulas presented here are applicable to all non-afocal (focal) telescopes, including particular types such as near point telescopes. All that is required for their evaluation is the positions of one pair of conjugate planes, the corresponding magnification, and the lens separation. The formulas can be used to estimate such quantities as a working or useful depth of field and accommodation demand, particularly when the optical system is not used at its design conjugates. A numerical example is presented.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Some 167 subjects showing anisometropia of at least 2 D, were selected from the records of the eye clinic of the Ramathibodi hospital in Bangkok, Thailand, and 472 subjects showing anisometropia of at least 1 D were selected from the clinic records of the Indiana University, School of Optometry. The incidence of amblyopia (20/30 or less) was found to be 100% among least meridional hyperopic anisometropes of 3.5 D and greater, and among myopic anisometropes of 6.5 D and greater. Lower levels of anisometropia showed a smaller proportion of amblyopia. Comparable results were obtained for anisometropes computed in terms of mean spherical refractive error. Significant difference was not apparent for the Thai and American groups.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Because there are psychological and emotional problems, as well as optical ones, when patients are adapting to aphakic corrections, it is necessary for the optometrist to establish rapport and provide suitable explanations. Suggestions are made concerning discussions about the optical changes associated with use of spectacles, implants, and contact lenses. The author advises the use of a cataract lens package in which a series of lenses is designed prior to cataract surgery.

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1979

数据来源: OVID